Water evaporates from boiling sap to make syrup. As the maple tree’s growing season gets hotter due to climate change, the sugar content of sap will decrease, requiring longer boiling and/or the use of reverse osmosis.
My mother and father raised me sugaring in the same sugarhouse that my grandfather built. On spring days when the sap was running, my parents, both full-time teachers, would pick us up after school to gather buckets. After gathering, we’d eat dinner at the sugarhouse. My father would stay up late into the night boiling with the radio on and our dog curled up asleep on the floor by the arch. On weekends when the sap was flowing, we’d boil all day long, with friends, family, and neighbors stopping by throughout the day. My parents are retired from teaching now, but they are still sugaring that same sugarbush in Hartland. As my family has continued to sugar that same forest, the forest–and sugaring itself–have changed.
In order for maple sugar sap to flow, temperatures need to freeze at night and thaw during the day. These freeze-thaw conditions are changing due to climate change; the annual number of unfrozen days has increased by about four days per decade since the 1970s. In Vermont, this has pushed sugaring season earlier than it historically was. The University of Vermont’s Proctor Maple Research Center found that the average sugaring season in Vermont now begins 8 days earlier than it did 50 years ago. You will hear this anecdotally when you talk to maple sugarers who have been in the business for a long time, or who inherited their sugarbush from families. My parents once tapped out during school break in February, but they have had to start earlier than that now If they want to catch the first run. The first boil of the year used to be in March but is now in February or even January. This also means that the sugaring season ends earlier than it once did. Overall, the season for sugaring is earlier, and actually slightly shorter, than it once was–Vermont has lost more than three days of the sugaring season over the past fifty years.
The geography of maple sugaring is also predicted to shift in the coming years due to climate change. By 2100, the region of maximum sap flow is predicted to shift northward by about 250 miles. The trees that remain here might not be as healthy due to drought and other stressors. Studies have shown that reduced snowpack—which is projected with warmer winters—can lead to root damage and reduce the growth of tree shoots. Sugar maples additionally do not tolerate saturated soils very well. As flooding events increase due to climate change, some of our maples might not be able to tolerate this saturated ground. Other threats include higher temperatures inhibiting sugar maple seed germination, which is best in cold temperatures, and competition from invasive species, which thrive in disturbed climates.
You were probably taught that it takes forty gallons of sap to make one gallon of maple syrup, however this isn’t always true. Climate change can affect the sugar content of sap because sugar content depends on the previous year’s growing conditions. The warmer the temperatures during the previous growing season, the fewer carbohydrate stored in sap, or the less sugar the next year. This is because trees have higher respiration rates (carbohydrate usage) with rising average temperatures, compared to photosynthesis (carbohydrate storage). One study predicts that maple sap’s sugar content will decline by one third by 2100. It will take more boiling time and a higher volume of sap to continue to make the same amount of syrup.
Despite these current and future challenges, Vermont’s maple syrup production continues to increase. This is not only due to the number of taps increasing; it is also due to new technology. Taps and tubing is better designed now, and many sugar makers use vacuum systems that actively pump sap from trees, greatly increasing yield. Many operations also use reverse osmosis, which removes water from sap by forcing it through porous membranes, leaving behind sap with a more concentrated sugar content. When this sap is boiled, it takes less time and energy to create maple syrup. As the challenges of climate change continue to impact Vermont’s sugaring industry, dedicated sugar makers are working to adapt to these changes.
I consider myself incredibly lucky to have grown up on a small sugaring operation. I learned the importance and joy that is found in hard work, family, community, and making food. I can only wish the same for future generations of Vermonters.
What you can do:
•Buy syrup with U.S.D.A. Organic and Bird-Friendly Maple designations. These designations ensure that sugar bushes are managed sustainably, and in a way that maintains forest diversity.
•Follow the Vermont Natural Resources Council (VNRC) and Vermont Public Interest Group (VPIRG) to learn how you can support climate action in Vermont.
